1. Technical Field
The present disclosure relates to magnetic fasteners, and more particularly to a magnetic fastener which is configured to contain the magnetic field and reduce leakage thereof.
2. Background of the Related Art
There have been many attempts to develop a commercially successful magnetic fastener for use in various applications such as for handbag closures. Included among these attempts are U.S. Pat. Nos. 2,812,203, 2,884,508, 3,372,443, 3,618,174, 3,919,743, 4,455,719, 4,458,396, 4,231,137, 4,754,532, 4,825,526, 4,021,891, 4,700,436, 4,453,294, 5,042,116, 5,142,746, 5,274,889, 5,251,362, 5,400,479 and 5,379,495.
For convenience of explanation of prior art fasteners, such fasteners are illustrated generally in FIG. 1 to which reference is being made. One disadvantage of presently known fasteners is that they fail to effectively contain the leakage of lines of magnetic flux both when the fastener is open as well as after the fastener is in the closed position. For example, referring to FIG. 1, for a magnetic fastener 10 manufactured as described in certain of the above listed patents, substantial magnetic flux leakage 12 radiates in all directions from magnet 14 with the primary leakage being laterally or radially around the perimeter of the magnetic fastener 10. This radial leakage occurs because there is no provision to contain magnetic flux lines 12 in a closed path around the periphery of fastener 10 and thus the lines of flux 12 extend out and around to the back of both the male plates 16 and female plates 18. Such leakage may cause damage to devices such as credit cards, computer disks and other items which store information or magnetic media.
Second, the above referenced fasteners depend primarily upon magnetic attraction to keep their parts in the closed position while using other means to prevent lateral movement and thus disengagement. The problem of lateral movement in all of the above fasteners is in part solved by the placement of pin 20 or other protrusion on at least one of the parts which fits into a receiving hole 22 defined in the other part 18 (FIG. 1). However, this configuration is not sufficiently effective when a lateral force is applied to the two parts of the fasteners, and the pin is moved off center relative to the corresponding pin on the second part of the fastener. This misalignment weakens the magnetic connection between the two parts. U.S. Pat. No. 5,042,116 to Ossianni attempts to stop this movement with a counter-sinking pin which fits snugly into a recess in the opposing pin. This arrangement requires difficult and costly manufacturing of the pins. Even the smallest amount of dust or magnetically attractive sand in the receiving recess will prevent the pin from seating properly, which weakens the magnetic circuit and thus the holding power of the fastener.
Magnetic fasteners, such as those described in the above patents, are primarily used on items such as handbags, which presents additional design problems. For example, at least one part of the fastener is affixed to a somewhat flexible member, such as the flap of the bag. This further decreases the holding strength of the fastener when a lateral separating force is applied to such fastener. Upon such application of lateral force to the fastener as described, the fastener rotates on its own axis until the attractive force of the magnet is no longer perpendicular to the long axis of the pin, which is oriented at a right angle to the face of the magnet. Because the magnetic attracting force is centered through the pin and at a right angle to the face of the magnet, when this rotation occurs, less force is required to disengage the two parts.
Further, when lateral force is applied to the currently available commercially successful magnetic fasteners, the pin may slide to the side of the hole and ride up and over the rim of the hole. This movement changes the direction of resistance from a line perpendicular to the face of the magnet (the angle of the greatest resistance to separation) to an arc or angle of less than 90.degree. to the face of the magnet (a direction of lessened resistance to separation).
The present invention relates to a magnetic fastener which avoids the above described problems by encapsulating the lines of magnetic flux which radiate from the magnet. The fastener also incorporates further mechanical attachment to augment the magnetic attraction of the magnetic fastener.